This article proposes a series compensator with unbalanced voltage sag ride-through capability applied to grid-connected induction motors. A conventional three-phase voltage source inverter (VSI) is intended to regulate the motor voltages. The VSI is connected in series with the grid and a three-phase machine with open-ended windings. The proposed system is suitable for applications in which no frequency variation is required, like large pumps or fans. The VSI dc-link voltage operates as a floating capacitor through the energy minimized compensation (EMC) technique, in which there is no dc source or injection transformer. The motor load condition determines the minimum grid voltage positive component (sag severity) to keep EMC operation. Meanwhile, a voltage unbalance may increase the dc-link voltage requirements. A 1.5-hp four-pole induction motor has been used to verify the ride-through capability of the proposed compensator under grid voltage disturbances. A total harmonic distortion (THD) analysis of grid currents demonstrates that the proposed system provides low THD even if no passive filter is used. The operating principle, converter output voltage analysis, pulsewidth modulation technique, control strategy, and components ratings are discussed as well. Simulation and experimental results are presented to demonstrate the feasibility of the system.

中文翻译：

---

不平衡电压暂降下使用浮动DC-Link转换器的并网感应电动机

本文提出了一种具有不平衡电压突降穿越能力的串联补偿器，该串联补偿器适用于并网感应电动机。传统的三相电压源逆变器（VSI）旨在调节电动机电压。VSI与电网和带有开放式绕组的三相电机串联连接。所建议的系统适用于不需要频率变化的应用，例如大型泵或风扇。VSI直流链路电压通过能量最小补偿（EMC）技术充当浮动电容器，其中没有直流电源或注入变压器。电动机负载条件确定了保持EMC运行所需的最小电网正电压分量（严重度下降）。同时，电压不平衡可能会增加直流母线电压要求。A 1。5 hp四极感应电动机已用于验证建议的补偿器在电网电压干扰下的穿越能力。电网电流的总谐波失真（THD）分析表明，即使不使用无源滤波器，所提出的系统也可提供较低的THD。还讨论了工作原理，转换器输出电压分析，脉宽调制技术，控制策略和组件额定值。仿真和实验结果表明了该系统的可行性。还讨论了转换器输出电压分析，脉宽调制技术，控制策略和组件额定值。仿真和实验结果表明了该系统的可行性。还讨论了转换器输出电压分析，脉宽调制技术，控制策略和组件额定值。仿真和实验结果表明了该系统的可行性。